Patient-tailored, central-vein catheters

ABSTRACT

The method of selecting and implanting a permanent venous catheter into a patient for use in chronic, extracorporeal blood treatment procedures. The method comprises determining the Body Surface Area of the patient. One then selects a permanent venous catheter having an actual length which is within 10% of a desired length as indicated in a Table found in this application for the Body Surface Area of the particular patient and a particular vein through which the catheter is to extend. Also, the internal diameter of the tubing is preferably adjusted in a manner correlating with the catheter length. Following catheter selection, the venous catheter is implanted in the venous system of the patient with the distal tip of the catheter being in or adjacent to the upper right atrium of the heart.

BACKGROUND OF THE INVENTION

Jugular and subclavian catheters are intended as a permanent bloodaccess for fluid delivery into the blood stream or egress of blood.Although these catheters may be used for various purposes includingtreatment of acute renal failure, they are essentially intended fortreatment of chronic renal failure. The invention will decrease therates of thrombosis and infections and prolong the overall survival ofthe catheters.

There are numerous manufacturers producing various implantablecatheters, and the line of products is changing every year. An extensivereview of all available catheters for acute and chronic hemodialysis waspublished in 1995 (Twardowski ZJ: Percutaneous blood access forhemodialysis. Seminars in Dialysis 1995; 8: 175-186).

Dual Lumen Catheters

These catheters are made of silicone rubber or polyurethane. Siliconerubber is less thrombogenic than polyurethane. Polyurethane isthermoplastic, while silicone rubber is thermoset and does not soften atbody temperature. Depending on the manufacturing process, the siliconerubber catheter may be made softer or harder, but is usually made soft.Most currently used catheters have dual lumens and are provided with asingle polyester cuff. Most dual-lumen catheters have a beveled inflowbore and a few side holes for inflow. Almost all catheters areradiopaque or are provided with radiopaque stripe.

The catheters are inserted transcutaneously through the subclavian orjugular veins using a peel-away sheath method or surgically through thejugular vein into the superior vena cava or right atrium. Femoral veinsare usually not used as a long-term access for hemodialysis. Jugularveins serve as a primary insertion site, because complication ratesassociated with insertion through the subclavian veins are significantlyhigher.

Although historically the catheters were inserted with variousapproaches, currently the catheter is usually inserted through theSedillot triangle (between the sternal and clavicular heads of thesternocleidomastoid muscle) using the Seldinger (Seldinger SI: Catheterreplacement of needle in percutaneous arteriography; new technique. ActaRadiol 1953; 39: 368-376) method. In this method the vein is puncturedwith a large bore needle and a guide wire is inserted into the veinthrough the needle. The needle is withdrawn, the skin tunnel is createdby a small incision, the entrance into the vein is prepared by adilator. The subcutaneous tunnel is created with a trocar, the catheteris inserted through the tunnel and introduced into the vein usingpeel-away sheath. Then the tip of the catheter is advanced through thebrachiocephalic vein into the superior vena cava or right atrium. Thesurgical method is similar, with the exception that the incision overthe Sédillot triangle is bigger and the vein is punctured under thedirect vision.

There are two method of subcutaneous tunnel creation. Because mostcatheters have an attached Y extension for connection with the dialyzerlines, the tunnel must be created from the skin exit to the site of thevein puncture (standard tunneling method). Another method, as describedin my previous patents (U.S. Pat. Nos. 5,209,723; 5,405,320; and5,509,897) requires that the catheter be tunneled from the vein puncturesite to the exit (reversed tunneling method). Such a method is possibleif the Y extension is attached to the catheter after the catheter ispulled through the exit. In both methods the subcutaneous tunnel iscreated over the clavicle; thus the catheter in the tunnel has more orless a reversed “U” shape.

Mutatis mutandis, an insertion through the subclavian veins is similarto that through the jugular veins. The puncture ofthe subclavian vein isdone just below the clavicle and slightly outside of the midclavicularline.

To prevent blood recirculation, most dual lumen catheters have inflowand outflow bores staggered approximately 2 cm, with outflow bore distalto that of inflow bore. Our studies (Twardowski Z J, Van Stone J C,Haynie J: All currently used measurements of recirculation in bloodaccess by chemical methods are flawed due to intradialyticdisequilibrium and/or recirculation at low flow Am J Kidney Dis 1998; 32(6): 1046-1058.) showed that at the high blood flow (over 300 mL/min)blood recirculation is only moderate, even in catheters with a flushtip. Various tip configurations aiming at decreasing clot formation werepatented (U.S. Pat. No. 5,509,897; 5,569,182; and 5,685,867).

Single Lumen Catheters

For subclavian vein catheterization, single lumen catheters were used in1969 (Erben J, Kvasnicka J, Bastecky J, Vortel V: Experience withroutine use of subclavian vein cannulation in haemodialysis. Proc EurDial Transpl Assoc 1969; 6: 59-64), a long time before two lumencatheters were invented. Canaud et al.(Canaud B, Béraud J J, Joyeux H,Mion C: Internal jugular vein cannulation using 2 silicone rubbercatheters: A new, simple and safe long-term access for extracorporealtreatment. Nephron 1986; 43: 133-138. Canaud B, Béraud J J, Joyeux H,Mion C: Internal jugular vein cannulation with two silicone rubbercatheters: a new and safe temporary vascular access for hemodialysis:Thirty months' experience. Artif Organs 1986; 10: 397-403.) decided tocontinue the method of Erben et al. using two single-lumen catheters,but they changed material from polyethylene to silicone rubber and usedjugular instead of subclavian vein insertion site. The catheters withinner/outer diameters of 2.0/3.2 mm had 6 side holes on the 5 distalcentimeters. The catheters were exteriorized by reversed tunneling (fromthe cervical incision to the skin exit), and extension-tubing adapterswere attached to the catheters after their externalization. Thecatheters were not provided with cuffs.

An important advantage of single catheters is its smaller entrance intothe vein and smaller exit site. With the smaller entrance it is morelikely to be able to cannulate the vessel repeatedly. The smaller exitis less prone to infections; however, infections were the most commoncomplications of long-term jugular vein catheters (Canaud B. Leray H.Béraud J J. Mion C. Acces vasculaire temporaire: du peripherique aucentral, du temporaire au permanent. [Temporary vascular access: fromperipheral to central, from temporary to permanent]. Nephrologie. 1994;15: 53_(—)9.). It is worth stressing that these catheters were notprovided with cuffs.

Single lumen catheters for single needle dialysis were developed in thelate 1980's. A regular, Tenckhoff peritoneal dialysis catheter was usedby Liggett et al. (Liggett R A, Kearney M M: Tenckhoff catheter as aprimary hemodialysis vascular access. Dialysis & Transplantation,1988;17: 522-524, 546.) Thrombotic complications of this catheter werefrequent as an anticoagulant was leached out of the tip through sideholes. A single, silicone rubber catheter with fish-mouth tip to preventsucking against the vessel wall was developed by Bionic Company(Friedrichsdorf, Germany) and the results with this catheter werereported by Demers et al. (Demers H G, Siebold G, Schielke D J, MuellerW, Niemeyer R, Hoeffler D: Soft right atrial catheter for temporary orpermanent vascular access. Dialysis & Transplantation, 1989; 18:130-139.) The catheter had a single polyester cuff as a barrier toperiluminal bacterial penetration, and no side holes at the tip to avoidsucking of the intima and/or leaching out of anticoagulant.

Tesio et al. (Tesio F. De Baz H. Panarello G. Calianno G. Quaia P.Raimondi A. Schinella D. Double catheterization of the internal jugularvein for hemodialysis: indications, techniques, and clinical results.Artif Organs. 1994; 18 :301_(—)4.) used catheters very similar to thoseof Canaud. These were silicone rubber catheters with internal/externaldiameters of2.0/3.2 mm and provided with 6 side holes on the 4 distalcm. Unlike Canaud catheters, Tesio catheters were provided with a 1 cmolive-like device to better fix the cannula in the tunnel. A recentmodel of Tesio catheter is provided with a small cuff (2 mm wide)located on the olive-shape device. Tesio et al. (Tesio F, De Baz H,Panarello G. Successful Long-term Central Venous Access. Home Hemo Int.1998; 2: 38-40) describe lower infection rates than that reported byCanaud et al.

Hybrid of Single and Double Lumen Catheter

A hybrid of single and dual lumen catheters, the Ash Split Cathwasrecently developed by Ash and his colleagues. The intravenous segment iscomposed of two separate D-shaped lumens, which have multiholedcylindrical tips (Mankus R A. Ash S R. Sutton J M: Comparison of bloodflow rates and hydraulic resistance between the Mahurkar catheter, theTesio twin catheter, and the Ash Split Cath. ASAIO Journal. 1998; 44:M532-4). The transcutaneous portion is a 14 French cylindrically shapedcatheter with D-shaped lumens and a polyester cuff. The cylindricaltranscutaneous part extends externally and connects through a hub withtwo transparent lumens attached to Luer lock Whereas the extravascularpart and the entrance to the vessel is similar in shape and function todual lumen catheters, the intravascular part is similar to single lumencatheters. The catheter is inserted with a single vein puncture. Twolumens in the vessel may have advantage over dual lumen by being moreflexible.

Hybrids of Subcutaneous and Percutaneous Devices

Two new devices that are hybrids of percutaneous and subcutaneousdevices were developed by Biolink Corporation (Middleboro, Mass.) andVascA (Topsfield, Mass.). The first device (Dialock™ Hemodialysis AccessSystem) consists of a port-like valve, implanted subcutaneously belowthe clavicle, which is connected to two single lumen catheters implantedinto the right atrium (Canaud B, My H, Morena M, Lamy-Lacavalerie B,Leray-Moragues H, Bosc J Y, Flavier J L, Chomel P Y, Polaschegg H D,Prosl F R, Megerman J. Dialock: a new vascular access device forextracorporeal renal replacement therapy. Preliminary clinical results.Nephrol Dial Transplant 1999; 14(3):692-8). For each hemodialysis theport is accessed with needle-cannulas, one for inflow, the other foroutflow. After dialysis the cannulas are removed and the whole deviceremains subcutaneously. The second device (LifeSite® Hemodialysis AccessSystem) consists of two subcutaneous valves with an internal pinch clampthat is actuated with a standard 14-gauge dialysis needle, eachconnected to a single lumen cannula placed in the central venouscirculation for hemodialysis. One valve with attached cannula is forblood inflow and the other is for blood outflow (Beathard G A, Posen G AInitial clinical results with the LifeSite® hemodialysis access system.Kidney Int. 2000 Nov;58(5):2221-7). The devices share the advantages anddisadvantages of both, subcutaneous and percutaneous blood accesses forhemodialysis.

Complications of Intravenous Catheters

There are two major complications of intravenous catheters: infectionand thrombosis. Both are at least partly related to the catheter design.

Infections

There may be exit site/tunnel infection, sepsis, and septicthrombophlebitis.

Measures Preventing Infections

Infection rates may be decreased by catheter design, implantationtechnique and postimplantation care. Here I will concentrate on catheterfeatures decreasing complications.

Material

Silicone rubber is a preferred material, because of its softness andhydrophobic (water repellant) properties.

Tunnel Length

The length of the tunnel is dependent on the catheter length outside ofthe vein. The longer the tunnel the less likely it is for themicroorganism to penetrate into the blood stream, but in a randomizedprospective study, tunneling alone of uncuffed catheters was not foundto decrease sepsis rates (von Meyenfeldt M M. Stapert J. de Jong P C.Soeters P B. Wesdorp R I. Greep J M. TPN catheter sepsis: lack of effectof subcutaneous tunneling of PVC catheters on sepsis rate. Jpen: JParenter Enteral Nutr 1980; 4:514-7). On the other hand the tunnelcannot be too long, so that the exit would not be too low on the chest.

Cuffs

The cuff constitutes a significant barrier for periluminal bacterialpenetration and the infection rates with the cuffed catheters aremarkedly lower than that with uncuffed catheters. There is no questionthat catheters without cuffs, both intravenous and peritoneal, areassociated with very high infection rates and are not suitable forchronic use. Catheter related sepsis was found to be more than ten timeshigher with uncuffed catheters as compared to cuffed catheters inpediatric population (Rovner M S, Brouhard B H, Cunningham J, Firor H:Comparison of cuffed vs. uncuffed catheters for extracorporeal therapyin pediatric patients. Dialysis & Transplantation 1992; 21: 513-522)Although there are no data on the relationship between the number ofcuffs and periluminal infection rates with intravenous catheter, suchdata exist for peritoneal catheters. A recent publication of the UnitedStates Renal Data System reported that compared to double-cuff catheterthe risk of peritonitis was 16 and 31% higher for single deep-cuff andsingle superficial-cuff catheters respectively. (U. S. Renal DataSystem, USRDS 1992 Annual Data Report, VI. Catheter-Related Factors andPeritonitis Risk in CAPD Patients. Am J Kidney Dis 1992; 5 (Suppl 2):48-54). Our own study found that the peritonitis rates were lower withtriple cuffed catheters compared to the double cuffed catheters(Twardowski Z J, Prowant B F, Nichols W K, Nolph K D, Khanna R: Six-yearexperience with swan neck catheter. Perit Dial Int 1992; 12:384-389).Exit site infections were also found to be lower with cuffed catheters.Rovner et al. (Rovner M S, Brouhard B H, Cunningham J, Firor H:Comparison of cuffed vs. uncuffed catheters for extracorporeal therapyin pediatric patients. Dial Transplant 1992; 21: 513-522) reported anexit infection rate of 1.26/1000 days, with cuffed catheters comparedwith a rate of 4.85/1000 days with uncuffed catheters. The reason forhigher infection rates with the absence of a cuff is poor immobilizationof the catheter that permits catheter movement outside the sinus whereit collects contaminants and transfers them deep into the sinus afterretraction. Also, catheter movement to and fro in the subcutaneoustunnel causes microtraumas predisposing further to infections.

Lumen Lock

Between hemodialysis sessions, it is customary to lock catheter lumenswith anticoagulant to prevent clot formation. Four anticoagulants havebeen used: heparin, urokinase, tissue plasminogen activator, and sodiumcitrate. Recently the locking solution has been provided also withantibacterial properties. For this purpose an anticoagulant has beenmixed with the antibiotic (Boorgu R, Dubrow A J, Levin N W, My H, CanaudB J, Lentino J R, Wentworth D W, Hatch D A, Megerman J, Prosl F R,Gandhi V C, Ing T S. Adjunctive antibiotic/anticoagulant lock therapy inthe treatment of bacteremia associated with the use of a subcutaneouslyimplanted hemodialysis access device. ASAIO J. 2000;46(6):767-70.) Noincompatibility was found in tests in vitro if heparin in finalconcentration of 5,000 U/mL was mixed with vancomycin, ceftazidime,cefazolin, or gentamicin (Vercaigne L M, Sitar D S, Penner S B,Bernstein K, Wang G Q, Burczynski F J. Antibiotic-heparin lock: in vitroantibiotic stability combined with heparin in a central venous catheter.Pharmacotherapy 2000;20(4):394-9.) If this method is used concomitantlywith systemic antibiotics for treatment of catheter related bacteremia,the method gives positive results without catheter removal in themajority of cases (Capdevila J A. Catheter-related infection: an updateon diagnosis, treatment, and prevention. Int J Infect Dis. 2(4):230-6,1998. —Sodemann K, Lubrich-Birkner I, Berger O, Baumert J, Feldmer B,von Hodenberg E. Gentamicin/sodium-citrate mixture as antibiotic-locktechnique for salvage and prevention of catheter-related infections—Afour year trial (abstract). J Am Soc Nephrol 8:173A, 1997.

Thrombosis

As early as in the mid 19^(th) century, Rudolf Virchow postulated thatthree factors predispose to phlebothrombosis (clot formation in thevein): hypercoagulable state, vein wall damage, and blood stasis. Thesethree factors are still judged to be the most important, and have to beconsidered in planning preventive measures. With a foreign body in theblood vessel, an additional factor becomes important: the material fromwhich this foreign body is made.

Measures Preventing Thrombosis

Thrombosis probably cannot be completely eliminated, but its incidencemay be reduced by catheter design and appropriate anticoagulation. Onlycatheter design features decreasing thrombosis rates will be discussedhere. These are: material, catheter shape and size, tip configuration,and number of lumens.

Material

Thrombogenicity of material is crucial in the speed of thrombusformation. Due to high thrombogenicity, prolonged catheterization wasimpossible with glass, polyethylene and polyvinyl cannulae. Polyurethaneis claimed to be less thrombogenic than tetrafluoroethylene. In animalstudies, silicone rubber catheters showed the lowest thrombogenicitycompared to catheters made of other materials (Welch G W, McKell D W,Silverstein P, Walker H L: The role of catheter composition in thedevelopment of thrombophlebitis. Surg Gynecol Obstet 1974; 138:421-442). Silicone rubber is a preferred material to preventcatheter-related thrombosis.

Insertion Site

The repeated damage to the intima seems to be crucial in thrombosis ofcannulated veins. A strong argument for this mechanism is more frequentand massive thrombosis seen with left sided cannulation where the veinpath is more tortuous (Ratcliffe P J, Oliver D O: Massive thrombosisaround subclavian cannulas used for haemodialysis (Letter). Lancet 1982;1: 1472-1473). In the series of Hoshal et al. (Hoshal V L Jr, Ause R G,Hoskins P A: Fibrin sleeve formation on indwelling subclavian centralvenous catheters. Arch Surg 1971; 102: 353-358) mural thrombi usuallyformed at the points where the catheter pressed on the vessel wall,particularly where the tip touched on the intima. In choosing theinsertion site these factors should be borne in mind. The jugular route,particularly on the right side, is advantageous since the course ofcatheter to the right atrium is almost a straight line, minimizingtrauma to the intima. The path from the left jugular vein is moretortuous. Subclavian veins are least favorable because of tortuouscourse, particularly on the left side. Besides, the narrow space betweenthe first rib and the clavicle, where the subclavian vein passes,predisposes to vein wall trauma when movement of the upper extremitiessqueezes the catheter. Cimochowski et al (Cimochowski G E, Worley E,Rutherford W E, Sartain J, Blondin J, Harter H: Superiority of theinternal jugular over the subclavian access for temporary dialysis.Nephron, 1990; 54: 154-161) stressed that vein stenosis is least likelyif the stiff catheter is inserted through the right jugular vein.Schillinger et al. (Schillinger F, Schillinger D, Montagnac R, MilcentT: Post catheterisation vein stenosis inhaemodialysis: Comparativeangiographic study of 50 subclavian and 50 internal jugular accesses.Nephrol Dial Transplant, 1991; 6: 722-724) evaluated phlebographicallythe rate of stenosis of the subclavian and/or brachiocephalic vein incases cannulated previously through the subclavian route or through thejugular route. They found a stenosis in 42% of the subclavian group andin 10% of the jugular group. The right side was cannulated in 58% ofcases in the subclavian group and 78% in the jugular group. The rate ofstenosis on the left side was higher, particularly in the jugular group(7.7% on the right and 18.2% on the left). It is worth stressing thatthe authors described the complications with use of stiff catheters.

Side Holes at the Distal End

All catheters for acute hemodialysis are provided with side holes at thedistal end. This is supposed to prolong catheter life, assuming thateven if the distal bore is occluded by a clot, a few side holes mayremain opened providing sufficient blood flow. Most catheters forchronic dialysis, both single and dual lumen, are also provided withside holes. There are no data in support of the notion that side holesprolong the life of chronic catheters. In my opinion the opposite may betrue. Firstly, many times, while removing chronic catheters, eitherelectively or because of catheter obstruction, a clot is found attachedto the tip of the catheter and anchored in the side hole of the inflowlumen. Such a clot is difficult to remove or dissolve while in situ.Secondly, intraluminal clot is usually easily removed or dissolved(Twardowski Z J: High-dose intradialytic urokinase to restore thepatency of permanent central vein hemodialysis catheters. AJKD 1998; 31(5): 841-847). The clot, which is difficult to remove is formed on theouter surface of the catheter and extends to the inside lumen. If so,the holes have no role in extending the life of the catheter. Thirdly,the heparin solution, which is instilled to the catheter lumen at theend of dialysis, may not reach the catheter tip and/or be leached out inthe period between dialyses, thus, predisposing to clot formation at thetip of the inflow lumen. Finally, if the inflow bore is occluded and theblood flows through the side holes, it is likely that the vein intima issucked into the holes, becomes damaged and causes formation of the clotin the vessel lumen. In such a case these holes would not be beneficialfor the catheter life, but maybe even precluding the possibility ofinserting another catheter into the same vein at a later time.(Twardowski Z J, Moore H L Side holes at the tip of chronic hemodialysiscatheters are harmful. Journal of Vascular Access 2001; 2(1): 8-16).

Shape of the Catheter

It is very likely that the major reason of these complications ispressure of the straight catheter on the vein intima at the “pressurepoints” where venous path takes a rapid turn. This led us to design aso-called “vein shape catheters”, which has been patented (U.S. Pat.Nos. 5,209,723; 5,405,320; 5,509,897; 5,569,182; and 5,685,867). Theidea of these catheters is to make the shape of the catheter as similaras possible to the shape of vein where the catheter is located; however,it is difficult to choose the catheter with the shape similar to that ofthe vein.

Size of the Catheter

Companies manufacturing catheters make them in a few sizes. Forinstance, Kendall Healthcare (Mansfield, Mass.) makes three sizes ofPermCath straight catheters: 36 cm, 40 cm, and 45 cm. The length of thecatheter is a total length, from the tip to the luer lock end. BARD(Salt Lake City, Utah) makes three sizes of permanently bent catheters:19 cm, 23 cm, and 27 cm. The length of the catheter is from the tip tothe cuff. The catheters of the same type have the same internaldiameter, regardless of their length. This practice causes that theshorter catheters have higher blood flow at the same inflow pressurethan the longer catheters.

This approach has disadvantage, as longer catheters, inserted inpatients with larger body build, should have higher blood flow toachieve a desired efficiency of dialysis. According to the DialysisOutcome Quality Initiative (DOQI) recommendations, all patients shouldhave delivered Kt/V of 1.2-1.3. (NKF-DOQI clinical practice guidelinesfor hemodialysis adequacy. National Kidney Foundation. Am J Kidney Dis.1997; 30(3 Suppl 2):S15-66.) Kt/V is a product of dialyzer clearancemultiplied by time of dialysis and divided by volume of distribution ofurea or total body water. Total body water is roughly proportional tothe body height and weight (Watson P E, Watson I D, Batt R D. Total bodywater volumes for adult males and females estimated from simpleanthropometric measurements. Am J Clin Nutr. 1980;33(1):27-39.) andclearance is proportional to the blood flow within certain limitsdepending on the dialyzer mass transfer area coefficient. Thus, tosatisfy DOQI requirements, longer catheters, inserted into largerpatients, should have higher, not lower, blood flow.

Poiseuille's equation predicts that, in circular tubes, at the samepressure difference and catheter length, the laminar flow isproportional to the 4^(th) power of the radius. On the other hand, thecatheter diameter cannot be too large to fill the vein too tightly as itpredisposes to the damage of vein wall, vein thrombosis and stenosis[Dixit A, Ram S, Zaman F, Pervez A, Torres C, Work J. Does the Ash splitcatheter have a better survival than the Mahurkar catheter? J Am SocNephrol 10: abstract A1042, 1999, Davenport A. Central venous cathetersfor hemodialysis: How to overcome the problems. Hemodial Int 4:78-82,2000.] The availability of only a few sizes of the catheters create aproblem of locating the catheter tip in an appropriate point in patientsof different body builds. Most catheters have internal diameter of 2 mm(PermCath—Kendall Healthcare, Opti-flow (BARD), Tesio—MedComp,Harleysville, Pa.) or 2.2 mm (Dialock—Biolink Corporation,LifeSite—VascA) regardless of catheter length.

For the best performance the tip of a central vein catheter forhemodialysis should be located in the right cardiac cavities [Jean G,Chazot C, Vanel T, Charra B, Terrat J C, Calemard E, Laurent G. Centralvenous catheters for hemodialysis: looking for optimal blood flow.Nephrol Dial Transplant 12(8):1689-91, 1997]. Schwab and Beathardrecommend catheter tip localization in the middle of the right atrium,while the patient is supine, so it will move no higher than to the lowersuperior vena cava while the patient is upright [Schwab S J, Beathard G.The Hemodialysis Catheter Conundrum: Hate Living with Them, But Can'tLive Without Them.] (Kidney Int. 1999; 56: 1-17). Both too high and toolow positions of the catheter tip are unfavorable. The heart moves downin the upright position and up in the supine position. Because thecatheter length is fixed, the catheter moves deeper into the rightatrium, while the patient is supine, and closer to the brachial veins,while the patient is upright. Breathing also influences catheterposition. During deep inspiration the diaphragm and the heart move downso the catheter tip moves up; during expiration the movements are inopposite directions. Finally, the chest wall subcutaneous tissue movesdown when the supine person assumes the erect posture (Schwab S J,Beathard G. ibid) The catheter cuff, which is anchored in this tissue,pulls the catheter tip upward.

If the catheter tip is located high in the superior vena cava it maytranslocate to one of the brachiocephalic veins where the blood flow isinsufficient to secure adequate blood flow through the dialyzer. If thecatheter tip is too low it may move to a cusp of the thebesian oreustachian valve, or migrate to the inferior vena cava or to the rightventricle. All this positions are unfavorable for catheter function. Thecatheter tip in the inferior vena cava gives apparently paradoxical lowrecirculation values with reversed lines (Twardowski Z J, Nichols W K,Van Stone J C, Haynie J: All currently used measurements ofrecirculation in blood access by chemical methods are flawed due tointradialytic disequilibrium or recirculation at low flow. Am J KidneyDis 32 (6): 1046-1058, 1998.) and provides high recirculation valueswith standard direction of lines. If catheter migrates to the rightventricle, it may become entangled in the papillary muscles and becomeobstructed (Twardowski Z J: Nichols W K: Opti-flow catheter tiptranslocation from the right atrium to the right ventricle. Journal ofVascular Access 2001; 2(1): 17-19. Too low position of the catheter tipin the right atrium predisposes to formation of the right atrialthrombus ([Gilon D, Schechter D, Rein A J, Gimmon Z, Or R, Rozenman Y,Slavin S, Gotsman M S, Nagler A. Right atrial thrombi are related toindwelling central venous catheter position: insights into time courseand possible mechanism of formation. Am Heart J. 135(3):457-62, 1998.Korones D N, Buzzard C J, Asselin B L, Harris J P. Right atrial thrombiin children with cancer and indwelling catheters. J Pediatr128(6):841-6, 1996). All these problems require that a catheter lengthbe precisely selected for a patient. I believe that the best compromisebetween conflicting requirements is to locate the catheter tip in theupper right atrium (URA).

Optimal Lengths and Diameters of Catheters

A study in 31 volunteers of large upper body veins using magneticresonance imaging showed a great variability in vein dimensions andshapes even in persons with the same body build. (Twardowski, Z J andSeger R M: Dimensions of central venous structures in humans measured invivo using magnetic resonance imaging: Implications for central veincatheter dimensions The International Journal of Artificial Organs, Vol.25, 2, 2002, pp. 107-123). In this study, the shapes and distances fromthe insertion sites in jugular and subclavian veins to the right atriumwere determined and correlated with the height, acromion-distance,weight, body surface area, and combinations thereof.

The tip of the dual lumen, straight catheters such as VasCath™ (BARD,Salt Lake City, Utah, USA) or PermCath® (Kendall Healthcare, Mansfield,Mass., USA) may be properly positioned, if x-ray is used during catheterimplantation. Because straight catheters are prone to kinking afterimplantation, the manufacturers supplemented these catheters withpermanently bent catheters: Opti-Flow™ (BARD, Salt Lake City, Utah) orSwan Neck™ PermCath™ (Kendall Healthcare, Mansfield, Mass.). If thesecatheters are inserted through an internal jugular vein, the bend islocated over the clavicle. Although insertion through the internaljugular vein is preferred, the catheters may be inserted through thesubclavian veins. In these cases the bend is located below the clavicle.The length from the bend to the tip is essentially fixed; therefore thecatheter length should be selected for the patient. If there is noguidance as to the appropriate length of the bent catheter, the cathetertip maybe located too high or too low. For this purpose, the exactdimensions of the venous system in vivo should be known; otherwise thecatheter selection would be based on guessing and the tip maytranslocate later to the improper position (Twardowski Z J: Nichols, WK: Opti-flow catheter tip translocation from the right atrium to theright ventricle. Ibid.

A perfect position of the tip of the bent catheter could be achieved ifmagnetic resonance image were performed in a patient before catheterimplantation and the precise measurements were performed as described inthe methods section of the magnetic resonance imaging study [TwardowskiZ J and Seger R M: Dimensions of central venous structures in humansmeasured in vivo using magnetic resonance imaging: Implications forcentral vein catheter dimensions—unpublished, manuscript attached].Another approach would be to implant a catheter basing the selection onguessing and replace for another if the guess was wrong. Bothapproaches, however, would be costly and impractical. It is much moreconvenient for the operator to know the optimal choice of the catheterlength before the procedure. The ranges of vein dimensions with the samebody size are considerable. Fortunately the acceptable position of thecatheter tip ranges from the middle of the right atrium to the lowersuperior vena cava and the selection of a catheter guided by our studywill usually be adequate. The most practical and effective approach tothe selection of the appropriate catheter length is to take into accountbody surface area of the patient.

DESCRIPTION OF THE INVENTION

Accordingly, there is a need to determine for an individual patient aprecise optimum catheter length and inner diameter that would best suitthe patient as a permanent, implantable catheter. When optimum catheterdimensions are provided to the patient, the tip of the catheter willmore reliably stay in the upper right atrium, so that the catheter willfunction better. Also, thrombosis rates can be decreased, and theoverall catheter survival increased, by the selection and provision of aproperly sized catheter for the patient. Surprisingly, the desiredlength, and consequently the desired internal diameter of catheters,strongly correlate with the body surface area of the patient. In otherwords, a short, stocky patient and a tall, thin patient may have similarbody surface areas, and, surprisingly, may have optimum catheter lengthsfor a particular implantation that are similar.

In accordance with this invention, a method is provided for selectingand implanting a permanent, venous catheter into a patient for use inchronic extracorporeal blood treatment procedures. The steps of themethod comprise:

1. Determining the body surface area (BSA) of the patient. This is aknown medical procedure, and it maybe determined in customary manner, topreferably obtain the body surface area in square meters.

2. One then selects a permanent venous catheter having an actual lengthfrom the catheter distal tip to its integral, proximal end which iswithin 10% of a desired length, typically in cm, as indicated in Table Ibelow for the body surface area (BSA) of the particular patient, and aparticular vein through which the catheter is to extend: namely theright internal jugular vein (RIJV); the right subclavian vein (RSCV);the left internal jugular vein (LIJV); or the left subclavian vein(LSCV):

TABLE I DESIRED LENGTH (cm.) BSA RIJV RSCV LIJV LSCV m² cm cm cm cm 1.2022.6 23.5 25.1 26.6 1.25 23.0 24.0 25.6 27.1 1.30 23.4 24.4 26.0 27.61.35 23.8 24.8 26.5 28.1 1.40 24.2 25.3 26.9 28.5 1.45 24.6 25.7 27.429.0 1.50 25.0 26.1 27.8 29.5 1.55 25.4 26.5 28.3 30.0 1.60 25.8 27.028.7 30.4 1.65 26.2 27.4 29.1 30.9 1.70 26.6 27.8 29.6 31.4 1.75 27.028.3 30.0 31.9 1.80 27.4 28.7 30.5 32.3 1.85 27.8 29.1 30.9 32.8 1.9028.2 29.5 31.4 33.3 1.95 28.6 30.0 31.8 33.8 2.00 28.9 30.4 32.3 34.32.10 29.7 31.3 33.2 35.2 2.20 30.5 32.1 34.1 36.2 2.30 31.3 33.0 34.937.1 2.45 32.5 34.3 36.3 38.5 2.60 33.7 35.6 37.6 40.0 2.75 34.9 36.839.0 41.4

3. As a final step, the venous catheter is implanted in the desiredvenous system of the patient, with the distal tip of the catheter beingin or adjacent to the upper right atrium of the heart.

Alternatively, a similar method for selecting and implanting a permanentvenous catheter into the patient may comprise the similar steps of: (1)determining the body surface area (BSA) of the patient; (2) selecting apermanent venous catheter having an actual length from the catheterdistal tip to the point on the catheter where it is to penetrate thewall of the desired vein into which it is to be implanted, said actuallength of the catheter being within 10% of a desired length as indicatedin Table 2 below for the body surface area (BSA) of the particularpatient and the particular vein through which the catheter is to extend(RJIV; RSCV; LIJV; or LSCV.)

TABLE 2 BSA RIJV RSCV LIJV LSCV m² cm cm cm cm 1.20 11.1 13.4 13.9 16.51.25 11.2 13.5 14.1 16.7 1.30 11.4 13.7 14.2 16.9 1.35 11.5 13.8 14.417.1 1.40 11.7 13.9 14.6 17.3 1.45 11.9 14.1 14.8 17.5 1.50 12.0 14.215.0 17.7 1.55 12.2 14.4 15.1 17.9 1.60 12.3 14.5 15.3 18.1 1.65 12.514.6 15.5 18.3 1.70 12.6 14.8 15.7 18.5 1.75 12.8 14.9 15.9 18.7 1.8012.9 15.1 16.1 18.9 1.85 13.1 15.2 16.2 19.1 1.90 13.2 15.3 16.4 19.31.95 13.4 15.5 16.6 19.5 2.00 13.5 15.6 16.8 19.7 2.10 13.8 15.9 17.120.1 2.20 14.2 16.2 17.5 20.5 2.30 14.5 16.5 17.9 20.9 2.45 14.9 16.918.4 21.5 2.60 15.4 17.3 19.0 22.1 2.75 15.8 17.7 19.5 22.7

3. As a third step, one implants the selected venous catheter in thedesired venous system of the patient with the distal tip of the catheterbeing in or adjacent to the upper right atrium of the heart.

As a further optional step, after selecting the desired actual catheterlength and the particular vein for implantation, one selects a desiredflow rate for the catheter, to obtain a catheter having an actual lengthwithin 10% of the desired length and an actual inner diameter within 3%of a desired inner diameter as indicated in Table 3 below, correlatedwith the actual length.

Desired tubing internal diameter in relation to tubing length atconstant flow/pressure relationship.

TABLE 3 Flow of Flow of Flow of Flow of 150-250 250-350 350-450 450-55Total ml/min ml/min ml/min ml/min Length Internal Internal InternalInternal (cm) diam. (cm) diam. (cm) diam. (cm) diam. (cm) 22 0.156 0.1720.185 0.196 23 0.157 0.174 0.187 0.198 24 0.159 0.176 0.189 0.200 250.161 0.178 0.191 0.202 26 0.162 0.180 0.193 0.204 27 0.164 0.181 0.1950.206 28 0.165 0.183 0.197 0.208 29 0.167 0.185 0.198 0.210 30 0.1680.186 0.200 0.211 31 0.170 0.188 0.202 0.213 32 0.171 0.189 0.203 0.21533 0.172 0.191 0.205 0.217 34 0.174 0.192 0.206 0.218 35 0.175 0.1930.208 0.220 36 0.176 0.195 0.209 0.221 37 0.177 0.196 0.211 0.223 380.178 0.197 0.212 0.224 39 0.180 0.199 0.214 0.226 40 0.181 0.200 0.2150.227 41 0.182 0.201 0.216 0.229 42 0.183 0.202 0.218 0.230

By way of clarification, the term “desired length” is a theoretical,perfect length for the catheter under the selected circumstances.However, in view of practicalities, the actual length of the catheter isof course the length of the actual catheter selected, which ispreferably within 10% of the desired length, and preferably within 5%thereof.

If desired, a catheter of known length maybe selected without recourseto body surface area, following which a desired catheter inner diametermaybe selected correlating with the actual length, depending upon theexpected flow rate through the catheter, in accordance with thisinvention.

Thus, a properly sized permanent, venous catheter may be selected andused for a particular patient and a particular site of implantation by asystem which correlates with the body surface area (BSA) of the patientto obtain an optimum catheter length, either a length that extends fromthe catheter distal tip to its integral proximal end or a length of thatportion of the catheter which is actually implanted in the particularvein. It should be added that the integral, proximal end of the catheterrepresents the end of the catheter without any detachable extensiontubes or the like, and which integral proximal end of the cathetertypically extends out through the skin of the patient after implantationby a short distance, for example, two to six cm. Then, as disclosed inmy previous U.S. Pat. No. 5,405,320 and others, an extension tube may beattached to the catheter proximal end, so that the regular and frequentcatheter connection and disconnection to hemodialysis sets can be madeagainst the extension tube. Then, when the extension tube wears out, itmaybe replaced, so that wear on the actual catheter itself is minimized.

With a properly selected catheter length for the particular patient andthe chosen site of venous implantation, one may select a desired flowrate through the catheter, and from that, one may select a desired innerdiameter dependent upon the actual length of the catheter, which innerdiameter optimally balances the desired flow rate through the catheterwith a minimum catheter diameter, to minimize interference with bloodflow in the vein by the implanted catheter, while providing adequate,desired blood flow through the catheter. In particular, longer cathetersmay, with the inner diameters proposed herein, have equal and properblood flow rates at normal pressures of hemodialysis when compared withshorter catheters.

In accordance with this invention, to select a catheter for one of thepermanent venous implantations as illustrated in FIGS. 1 and 2, one mayfirst determine the body surface area of the patient, for example by thewell-known method of DuBois et al.; Arch. Int. Med. 17: 863-871 (1916).

From the body surface area and the desired vein in which implantation isto be made (RIJV, RSCV, LIJV, or LSCV), one can determine the desiredlength in cm. in accordance with Table 1 or Table 2, depending uponwhich length of the catheter is desired to be used for catheterselection. Then, an optimum tubing inner diameter for the catheter maybe determined from the length of the catheter determined in the previousstep in accordance with Table 3. Based on this, an actual catheter maybe selected which is within 10% of the desired length and 3% of thedesired inner diameter. Such a catheter may be implanted, and willexhibit improvements with that particular patient over catheters ofdiffering dimensions. These improvements may comprise a decreasedprobability of atrial thrombosis, coupled with improved probability ofappropriate blood flow, optimization of blood flow, less vein thrombosisand stenosis, increased probability of adequate dialysis, improvedcatheter survival, and decreased patient morbidity.

If desired, one may correlate a catheter's length to its desired innerdiameter without regard to the body surface area of the patient. This initself can provide significant advantages of flow optimization.

Straight line interpolation from the various Tables may be used whenneeded.

Advantages and Disadvantages of Dual Lumen Catheters

The main advantage of dual lumen catheters is convenience of insertion.Instead of two punctures only one puncture is required. This decreasesthe insertion time considerably and may decrease complication ratesrelated to the insertion procedure itself. This feature was veryimportant when stiff catheters for acute dialysis were used because thecatheter was inserted for only a few days. For chronic dialysis thisfeature is less relevant, because the catheters are used for severalmonths or years and decrease of thrombotic and infectious complicationstakes precedence over convenience and complication rates duringinsertion. Besides, complication rates during insertion of softcatheters are very low.

The main disadvantage of dual catheters is their large diameter. Thelarger diameter the more damage to the vessel wall and the higherexit-site infection rates. As mentioned above, compared to single lumencatheter, dual lumen catheter is stiffer at the same durameter(hardness) of material. Consequently the damage to the pressure points(see above) is more pronounced.

Disadvantages of Single Lumen (Canaud and Tesio) Catheters

The major advantages of single lumen catheters are their smallerdiameter and better flexibility. This decreases damage to the vesselwall, vein intima, and decreases exit site infection rates. If bothcatheters are implanted into the same vein, then the total diameter oftwo catheters is bigger than that of dual lumen catheter. The advantageof smaller lumen shows only if the catheters are implanted through twoveins, e.g., jugulars on each side or jugular and subclavian on the sameside. It is worth stressing that the diameter of brachiocephalic veinsis bigger than diameter of either jugular or subclavian veins (Table 2).

In this invention, the catheters for long-term hemodialysis access areintended to be inserted into the upper right atrium through one of thefollowing veins:

1. Right internal or external jugular vein

2. Left internal or external jugular vein

3. Right subclavian vein

4. Left subclavian vein

The intravenous catheter of this invention comprises a flexible catheterbody, which may be made of medical grade polyurethane, silicone rubberor equivalent material. The catheter may have either single lumen or twolumens. The distal end portion defines flow tubing for bloodcommunication between the lumen and the vein. The tip of the cathetermay be provided with side hole(s), although preferably the holes shouldbe absent. The proximal end portion defines a flow tubing forcommunication with the extension set, which may be coupled with anyblood withdrawal and/or intravenous fluid delivery system, such ashemodialyzer, hemofilter, plasmapheresis apparatus, etc. The catheter ispreferably provided also with one or two cuffs (subcutaneous or externaland deep or internal), which are the bands of fabric affixed to thecatheter body (tubing) for fibrous tissue ingrowth in the cathetertunnel.

Implantation of the catheter may be performed either surgically in anoperating room or in a procedure room under sterile conditions. Afteranesthetizing the skin over the intended insertion site, a small, 1-3 cmskin incision is made and dissected bluntly closer toward the vein. TheSeldinger method of catheter insertion, already described above, is apreferred method of catheter insertion into the vein. The catheterlength and diameter is chosen according to the body size as shown in thetable below. A proximal end portion is then used as a gauge to mark thepositions of the external cuff and the exit. Using a small hemostat orother suitable instrument a tunnel is made from the incision to thelevel where the external cuff will lodge. A trocar with the externaldiameter identical to the catheter tubing is attached to the externalend of the catheter, passed through the exit site and the catheter ispulled through the exit. An extension set is then attached to thecatheter, and the catheter is covered with immobilizing dressing.Because the external cuff is bigger then the last portion of thesubcutaneous tunnel, the catheter cannot dislodge outside, thus noanchoring suture is needed at the exit site.

Relative to the human body after the implantation the catheter consistsof three segments: 1) intravenous catheter segment is the part of thecatheter located intravenously; the length of this part in relation tobody surface area is given in table 2; 2) intramural catheter segment isthe part of the catheter contained within the tunnel; and 3) externalcatheter segment is the part of the catheter outside the skin exit. Thecatheter tunnel is the passageway through the thoracic wall within whichthe catheter is contained. Internal tunnel exit is the inlet of thetunnel into the vein. Skin exit is the skin outlet of the tunnel.Subcutaneous or superficial or outer or external cuff is located close(1-3 cm) to the skin exit. The inner or deep cuff is located 2-6 cm fromthe external cuff, closer to the vein. The part of the tunnel betweenthe skin exit and the outer cuff constitutes the sinus tract.

The catheter may be made radiopaque by addition of barium sulfate orother suitable material into the catheter body. This will facilitatevisualization of the catheter on an X-ray.

Subcutaneous cuffs provide both bacteriological barrier against tunnelinfection and anchoring means of the intramural and external cathetersegments minimizing the movement of the catheter into and out of thetunnel. As mentioned above, such a movement predisposes to contaminationof the tubing with introduction of contaminants into the sinus tractafter its retraction. Downward directed skin exit for the catheterfurther decreases chances of sinus tract contamination with the downflowing sweat and bacteria laden water. Also, downward directed exitfacilitates pus drainage should infection occur.

The external segment of the catheter typically protrudes about 2 to 6cm., typically about three cm. out of the skin and may be attached to anextension set consisting of a connector having a flexible extensiontube, approximately 8 centimeters in length and equipped with a femaleluer lock adapter and sealing cap. The extension set is attached to thecatheter body after the catheter is inserted into the vein and thesubcutaneous tunnel is created. If the extension set is attached to thecatheter body before implantation, then the standard tunneling methodmust be used. During the connection procedure for fluid delivery and/orblood egress the extension tube is clamped, the cap is removed and anappropriate male A male luer adapter is coupled with the female luerlock adapter of the extension tube. After prolonged use, the extensiontube may be damaged to the extent that it has to be replaced. Theconnector facilitates the replacement without the necessity of thecatheter removal.

One single lumen catheter may be used for drug delivery, parenteralnutrition, and blood withdrawal for repeated laboratory tests. Althoughone catheter may be used for blood purification procedure (hemodialysis,plasmapheresis, hemofiltration, etc) two catheters are preferred, onefor inflow and one for outflow. If two catheters are inserted, the tipsof the catheters should preferentially be a few centimeters apart withthe outflow closer to the right atrium. Two catheters may be insertedthrough the same vein or through two veins. From the convenience pointof view it is better to insert both catheters through the same vein;however, to avoid damage of vein wall, vein thrombosis and stenosis thevein should not be filled too tightly, so it is better to insert thecatheters through two veins. Any combination of insertion sites may beused, e.g., one catheter inserted through the right internal jugularvein and the other through the left subclavian vein. As mentioned above,dual lumen catheters are more convenient from the insertion point ofview. The Tables above provide optimum lumen lengths for dual lumencatheters in the same manner as single lumen catheters.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a view of two single lumen catheters implanted in a patientthrough the left subclavian vein and left jugular vein.

FIG. 2 is a view of the dual lumen catheter implanted in a patientthrough the right jugular vein.

DETAILED DESCRIPTION OF THE INVENTION

As shown in FIG. 1, the catheter 10 enters the left internal jugularvein 12, and its tip 14 is located in the right upper atrium 25. Theexit 16 from tissue tunnel 17 is on the chest and the external part,3 cmlong, is protruding out of the skin. A known luer lock extension willgenerally be attached to the proximal catheter end 19 and the lumen 18.

Catheter 20 enters the left subclavian vein 22, and its tip 24 is alsolocated in the upper right atrium 25. The exit 26 from tissue tunnel 27is on the chest, and the proximal, external catheter part 31 protrudesabout 3 cm out of the exit 26. The external bore 28 of the catheter maybe attached to another luer lock extension. The catheter tip of thesubclavian catheter 24 is preferably slightly higher in this embodimentthan the other catheter tip 14, as it is intended for inflow.

The dual lumen catheter 30 in FIG. 2 enters the jugular vein 32 and itstip 34 is located in the right upper atrium 25 a. The end of the inflowlumen 42 maybe located about 0.5 cm. higher than the outflow lumen 44,particularly at flow rates under 300 ml/min. At higher flow rates, thecatheter end may preferably be flush if desired. The external catheterend part 37 protrudes about 3 cm out of the tunnel exit 36. The externalends of bores 42, 44 of the catheter may be connected to an extensiontube.

Before implantation, the catheters are selected in a manner dependent onthe patient body surface area and the implantation site. The outflowlumen bore 44 may end lower in the right atrium 25 a than the inflowbore 42.

To cover the whole range of body sizes in adult population, at leastnine lengths of the catheters should preferably be available. Cathetertips of single lumen catheters maybe located at the same level in theupper right atrium. Catheter diameters may be adjusted to the catheterlengths as previously described so as to provide standardized bloodflows.

The above has been offered for illustrative purposes only and is notintended to limit the scope of the invention of this application, whichis as defined in the claims below.

That which is claimed:
 1. The method of selecting and implanting apermanent venous catheter into a patient for use in chronicextracorporeal blood treatment procedures, which comprises: determiningthe Body Surface Area (BSA) of the patient; selecting a permanent venouscatheter having an actual length from the catheter distal tip to itsintegral, proximal end which is within ten percent of a desired lengthin cm. as indicated in the Table below for the Body Surface Area of theparticular patient and a particular vein through which the catheter isto extend (RIJV; RSCV; LIJV; or LSCV): DESIRED LENGTH (cm.) BSA RIJVRSCV LIJV LSCV m² cm cm cm cm 1.20 22.6 23.5 25.1 26.6 1.25 23.0 24.025.6 27.1 1.30 23.4 24.4 26.0 27.6 1.35 23.8 24.8 26.5 28.1 1.40 24.225.3 26.9 28.5 1.45 24.6 25.7 27.4 29.0 1.50 25.0 26.1 27.8 29.5 1.5525.4 26.5 28.3 30.0 1.60 25.8 27.0 28.7 30.4 1.65 26.2 27.4 29.1 30.91.70 26.6 27.8 29.6 31.4 1.75 27.0 28.3 30.0 31.9 1.80 27.4 28.7 30.532.3 1.85 27.8 29.1 30.9 32.8 1.90 28.2 29.5 31.4 33.3 1.95 28.6 30.031.8 33.8 2.00 28.9 30.4 32.3 34.3 2.10 29.7 31.3 33.2 35.2 2.20 30.532.1 34.1 36.2 2.30 31.3 33.0 34.9 37.1 2.45 32.5 34.3 36.3 38.5 2.6033.7 35.6 37.6 40.0 2.75 34.9 36.8 39.0 41.4

and implanting the venous catheter in the venous system of the patientwith the distal tip of the catheter being in or adjacent to the upperright atrium of the heart.
 2. The method of claim 1, further includingthe step of: after selecting said actual length for a catheter within 10percent of said desired length and said particular vein, selecting adesired flow rate of 150 to 250 ml. per minute; and obtaining a catheterhaving said actual length and an actual inner diameter within 3 percentof a desired inner diameter indicated in the Table below for the actuallength: TUBING INTERNAL DIAMETER IN RELATION TUBING LENGTH Actual Length(cm.) Inner Diameter (cm.) 22 0.156 23 0.157 24 0.159 25 0.161 26 0.16227 0.164 28 0.165 29 0.167 30 0.168 31 0.170 32 0.171 33 0.172 34 0.17435 0.175 36 0.176 37 0.177 38 0.178 39 0.180 40 0.181 41 0.182 42 0.183


3. The method of claim 2, in which said actual inner diameter is within2 percent of the desired inner diameter.
 4. The method of claim 1,further including the step of: after selecting said actual length for acatheter within 10 percent of said desired length and said particularvein, selecting a desired flow rate of 250 to 350 ml. per minute; andobtaining a catheter having said actual length and an actual innerdiameter within 3 percent of a desired inner diameter indicated in theTable below for the actual length: Actual Length (cm.) Inner Diameter(cm.) 22 0.172 23 0.174 24 0.176 25 0.178 26 0.180 27 0.181 28 0.183 290.185 30 0.186 31 0.188 32 0.189 33 0.191 34 0.192 35 0.193 36 0.195 370.196 38 0.197 39 0.199 40 0.200 41 0.201 42 0.202


5. The method of claim 4 in which said actual inner diameter is within 2percent of the desired inner diameter.
 6. The method of claim 1, furtherincluding the step of: after selecting said actual length for a catheterwithin 10 percent of said desired length and said particular vein,selecting a desired flow rate of 350 to 450 ml. per minute; andobtaining a catheter having said actual length and an actual innerdiameter within 3 percent of a desired inner diameter indicated in theTable below for the actual length: Actual Length (cm.) Inner Diameter(cm.) 22 0.185 23 0.187 24 0.189 25 0.191 26 0.193 27 0.195 28 0.197 290.198 30 0.200 31 0.202 32 0.203 33 0.205 34 0.206 35 0.208 36 0.209 370.211 38 0.212 39 0.214 40 0.215 41 0.216 42 0.218


7. The method of claim 6 in which said actual inner diameter is within 2percent of the desired inner diameter.
 8. The method of claim 1, furtherincluding the step of: after selecting said actual length within 10percent of said desired length and said particular vein, selecting adesired flow rate of 450 to 550 ml. per minute; and obtaining saidcatheter having an actual inner diameter within 3 percent of the desiredinner diameter indicated in the Table below for the actual length:Actual Length (cm.) Inner Diameter (cm.) 22 0.196 23 0.198 24 0.200 250.202 26 0.204 27 0.206 28 0.208 29 0.210 30 0.211 31 0.213 32 0.215 330.217 34 0.218 35 0.220 36 0.221 37 0.223 38 0.224 39 0.226 40 0.227 410.229 42 0.230


9. The method of claim 8 in which said actual inner diameter is within 2percent of the desired inner diameter.
 10. The method of selecting andimplanting a permanent venous catheter into a patient for use in chronicextracorporeal blood treatment procedures, which comprises: selecting adesired flow rate of 150 to 250 ml. per minute for a catheter to beimplanted in a patient; selecting a permanent venous catheter having anactual length from the catheter distal tip to its integral, proximal endof 22-42 cm., said catheter having a lumen with an actual inner diameterwithin 3 percent of a desired inner diameter indicated in the Tablebelow for the particular actual length: Actual Length (cm.) InnerDiameter (cm.) 22 0.156 23 0.157 24 0.159 25 0.161 26 0.162 27 0.164 280.165 29 0.167 30 0.168 31 0.170 32 0.171 33 0.172 34 0.174 35 0.175 360.176 37 0.177 38 0.178 39 0.180 40 0.181 41 0.182 42 0.183

and implanting the venous catheter in the venous system of the patient.11. The method of claim 10 in which said actual inner diameter is within2 percent of the desired inner diameter.
 12. The method of selecting andimplanting a permanent venous catheter into a patient for use in chronicextracorporeal blood treatment procedures, which comprises: selecting adesired flow rate of 250 to 350 ml. per minute for a catheter to beimplanted in a patient; selecting a permanent venous catheter having anactual length from the catheter distal tip to its integral, proximal endof 22-42 cm., said catheter having a lumen with an actual diameterwithin 3 percent of a desired inner diameter indicated in the Tablebelow for the particular actual length: Actual Length (cm.) InnerDiameter (cm.) 22 0.172 23 0.174 24 0.176 25 0.178 26 0.180 27 0.181 280.183 29 0.185 30 0.186 31 0.188 32 0.189 33 0.191 34 0.192 35 0.193 360.195 37 0.196 38 0.197 39 0.199 40 0.200 41 0.201 42 0.202

and implanting the venous catheter in the venous system of the patient.13. The method of claim 12 in which said actual inner diameter is within2 percent of the desired inner diameter.
 14. The method of selecting andimplanting a permanent venous catheter into a patient for use in chronicextracorporeal blood treatment procedures, which comprises: selecting adesired flow rate of 350 to 450 ml. per minute for a catheter to beimplanted in a patient; selecting a permanent venous catheter having aactual length from the catheter distal tip to its integral, proximal endof 22-42 cm., said catheter having a lumen with an actual inner diameterwithin 3 percent of a desired inner diameter indicated in the Tablebelow for the particular actual length: Actual Length (cm.) InnerDiameter (cm.) 22 0.185 23 0.187 24 0.189 25 0.191 26 0.193 27 0.195 280.197 29 0.198 30 0.200 31 0.202 32 0.203 33 0.205 34 0.206 35 0.208 360.209 37 0.211 38 0.212 39 0.214 40 0.215 41 0.216 42 0.218

and implanting the venous catheter in the venous system of the patient.15. The method of claim 14 in which said actual inner diameter is within2 percent of the desired inner diameter.
 16. The method of selecting andimplanting a permanent venous catheter into a patient for use in chronicextracorporeal blood treatment procedures, which comprises: selecting adesired flow rate at least 450 ml. per minute for a catheter to beimplanted in a patient; selecting a permanent venous catheter having anactual length from the catheter distal tip to its integral, proximal endof 22-42 cm., said catheter having a lumen with an actual inner diameterwithin 3 percent of a desired inner diameter indicated in the Tablebelow for the particular actual length: Actual Length (cm.) InnerDiameter (cm.) 22 0.196 23 0.198 24 0.200 25 0.202 26 0.204 27 0.206 280.208 29 0.210 30 0.211 31 0.213 32 0.215 33 0.217 34 0.218 35 0.220 360.221 37 0.223 38 0.224 39 0.226 40 0.227 41 0.229 42 0.230

and implanting the venous catheter in the venous system of the patient.17. The method of claim 16 in which said actual inner diameter is within2 percent of the desired inner diameter.
 18. The method of selecting andimplanting a permanent venous catheter into a patient for use in chronicextracorporeal blood treatment procedures, which comprises: determiningthe Body Surface Area (BSA) of the patient; selecting a permanent venouscatheter having an actual length from the catheter distal tip to thepoint on the catheter where it is to penetrate the wall of a desiredvein into which it is to be implanted, said actual length of thecatheter being within 10% of a desired length as indicated below for theBody Surface Area (BSA) of the particular patient, and the particularvein through which the catheter is to extend (RJIV; RSCV; LIJV; orLSCV): BSA RIJV RSCV LIJV LSCV m² cm cm cm cm 1.20 11.1 13.4 13.9 16.51.25 11.2 13.5 14.1 16.7 1.30 11.4 13.7 14.2 16.9 1.35 11.5 13.8 14.417.1 1.40 11.7 13.9 14.6 17.3 1.45 11.9 14.1 14.8 17.5 1.50 12.0 14.215.0 17.7 1.55 12.2 14.4 15.1 17.9 1.60 12.3 14.5 15.3 18.1 1.65 12.514.6 15.5 18.3 1.70 12.6 14.8 15.7 18.5 1.75 12.8 14.9 15.9 18.7 1.8012.9 15.1 16.1 18.9 1.85 13.1 15.2 16.2 19.1 1.90 13.2 15.3 16.4 19.31.95 13.4 15.5 16.6 19.5 2.00 13.5 15.6 16.8 19.7 2.10 13.8 15.9 17.120.1 2.20 14.2 16.2 17.5 20.5 2.30 14.5 16.5 17.9 20.9 2.45 14.9 16.918.4 21.5 2.60 15.4 17.3 19.0 22.1 2.75 15.8 17.7 19.5 22.7

and implanting the venous catheter in the venous system of the patientwith the distal tip of the catheter being in or adjacent to the upperright atrium of the heart.